I have had a couple UAD-1 cards for several years now. UA is continuing to improve and expand the range of plugins available. They just signed an exclusive agreement with AMS Neve Limited to co-develop a series of classic console plug-ins for the UAD-1 plugin. The first of which, will be the 1073 EQ.
They just completed the Roland bundle (Space Echo should be out anytime now) and also the Precision Mastering series. I would not be surprised to see more plugins of UA hardware, in the future. Did anyone say LA-3A? Of course, the current catalogue of plugins is pretty impressive. My favorite's being, many of the vintage classics, like the LA-2A, 1176LN, Pultec Pro & EMT Plate 140. Yes, the track freeze function works great, in SONAR, using the UAD-1 plugins. It automatically releases the cards DSP, for more plugins, once you freeze. If you are on a tight budget (aren't we all) then the Project Pak is the most economical. But the best bang for buck, right now is probably the new Flexi-Pak.
If you shop here for your UAD-1, you can get a 10% discount, by being a registered member, of the UAD-1 forum. You can pick up a Flexi-Pak for about $630 delivered(less discount). Which means you basically get the UAD-1 for $130, cause you still have $500 dollars left to spend on more plugins. If I were is your shoes and I was getting the Flexi-Pak, as a first UAD-1 purchase, I would get these plugins with my coupon (LA-2A, 1176LN, Pultec Pro & EMT Plate 140)
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http://www.jrrshop.com/product_info.php?products_id=5531 UAD-1 forum:
http://www.chrismilne.com/uadforums/ You can easily check out the various plugins, by double clicking on the plugin GUI, that interests you and clicking on the "Demo's & Tips" to the left, for the plugin. Most have audio & video demos:
http://www.uaudio.com/products/software/UAD-1/index.html There are some motherboard/chip set combinations that are more problematic than others. It may behoove you to contact UA directly (call or email) with your computer specs, for the latest info first. Be aware, that you may need to get your hands "dirty" (changing PC slots, setting PCI latency, etc) to fine tune the UAD-1, for use in your PC.
http://www.uaudio.com/support/software/UAD-1/motherboards.html Cheers