So I've decided to buy BFD3... I was thinking about getting the Neil Peart expansion pack. Any opinions about this expansion pack? Are there better ones out there? I play heavy rock, mainly. Any opinions would be appreciated!

Get BFD3 itself first, then consider expansions. The included DW kit is really, really good in my opinion. You may not find you want for anything else.

Check out platinum samples expansions for heavy music. Fxpansion also have a boatload. The sonic reality stuff has its own sound, but minus the new nick mason pack, doesn't have direct channels on the cymbals, so it doesn't mix and match great with other packs. I love evil drums from platinum samples recorded by Joe baresi.

Joe Baresi's Evil Drums is also my favorite for heavy rock, but I'd check out all of the sample tracks they have at Platinum Samples.  They have other kits that are great and I'm sure you'll find your perfect match. 
 
I have the Peart kit and it definitely has its own sound that I haven't found as useful as I had hoped.  To me it sounds more light rock than heavy.  i kind of wish I hadn't wasted my money on it, even at the 50% of sale price I paid for it.

I got the Neil Peart volume 1 and was very disappointed, no direct channels for the cymbals is very poor and I'm just glad I only paid $19 for it. As Sycraft said, get to know the kits that come with BFD3 first and then if they're not what you're after you can think about expansions.
The 7 kits that come with BFD3 are all from platinum samples and you wont find any better samples than theirs right now.
 
Steve

Thanks guys for your input! I appreciate your help! I was about to drop the coin on the Peart kit, so I'm glad I asked! I'll definitely check out the platinum samples and the Baresi stuff. Thanks again for your helpful suggestions.

I have ECO and BFD2. IS there any compelling reason to upgrade to BFD3? It's a lot of money and my drum library is building up. I already have Battery 3,4, addictive drums, Abbey Road 60's drummer and Studio Drums for Kontakt. Am I really missing anything by skipping BFD3?

http://www.fxpansion.com/uploadedFiles/BFD3_Whats_New.pdf
 
I'm definitely going to upgrade as soon as I get a job 
 
For a heavy kit there are at least a couple on the FXpansion website - there's the Heavy Expansion pack, and also the Dunnett Titanium kit - both are worth checking out

ampfixer
I have ECO and BFD2. IS there any compelling reason to upgrade to BFD3? It's a lot of money and my drum library is building up. I already have Battery 3,4, addictive drums, Abbey Road 60's drummer and Studio Drums for Kontakt. Am I really missing anything by skipping BFD3?

I dunno with BFD2, since I don't have that. However over BFD Eco, which I do have, ya there is a lot of improvement. The two big things for me are great sound, and the ability to build massive kits. As I said in another thread I want all of the drums, all of the times :). I have set up a kit with 6 toms, 2 snares, 2 BDs, about 7 cymbals and some auxiliary percussion. Makes me quite happy. Ya you'd need to be an octopus to play it, whatever, that's why we are doing it on a computer :).
 
I find the sound is really good and the kit is really playable too. For example the drums are recorded with a massive dynamic range, tons of velocity layers. Often this is problems in practice but not here. For one, they are all mapped properly, so low velocity is quiet, high velocity is loud. No uneven mapping (that I've found). Then there's the fact that they have it set up with a good medium limiter on the master bus by default. This means you don't have to fiddle with the volume generally. Just go. Your bass drums will get some big peaks, but it'll deal with it and sound good. If you go real loud or real soft, ya you may need to make some adjustments, but by default it works, and without any fuss.
 
So that's why I like it. If BFD2 offers that kind of stuff, then I would probably be just as happy with it. If not, then I'd want BFD3 for sure.

It's definitely worth the upgrade price but if you can't afford it, you can't afford it.
I think given that there are 5 new kits (7 if you include the fact the one kit is played with both mallets and brushes) that come from one of the very best sample library producers out there, then the upgrade cost is very much worth it. Those 7 kits would cost you a lot more than $149 if you were to buy them as an expansion pack.
 
Whilst you might think think the new UI is not as pretty as BFD2 it's no certainly pig in lipstick
I didn't like it at first but the layout is much quicker and easier to use than BFD2 and is more like BFD Eco in a way.
 
I could go on and echo the above posts but the fact that FXpansion have just released the BFD3 Demo this week gives you the opportunity to find out for your self what's so good about it. Don't forget there will of course be limitations with the demo but it should give you a good idea about it's new features.
 
Your old kits won't sound any better in BFD3 so if you're happy with BFD2 I'd say there was no rush to upgrade, wait to you can afford it and get to know the demo as it's a deep program that does a lot more than other drum VSTi's.
I think there was something like a 5 year gap between BFD2 and BFD3 so you should have plenty of time
 
Steve