I have friends that use UAD plugins and I've had the liberty to use them myself.
Quality mate! The EMT 240&140 are beautiful.
I heard it's totally worth the money. I just invested in iLok this summer. Gotta say...I love the Waves and Slate Digital stuff I'm running : ) and even if Waves is a bit hype, for the prices they've been selling stuff at lately O_O
I recently got like 500 bucks worth of Waves stuff for like 150.
Um if you can afford it then get it. But remember you have to purchase the plugins that work with the UAD line separately, the pci hardware is basically a small computer which hosts the software. Fatso is the most bad ass software compressor I have ever heard, it sounds better than most hardware compressors under $1,000 due to its tonal characteristics. The tape recorder is also really really sick. I have only used those 2 extensively but I know the eq is also great and you don't tax your ram or cpu to use this stuff. Waves cannot hold a candle to the UAD hardware, there is no comparison at all really. In fact the only thing that can compete with UAD stuff is real high end rackmount gear so Id say you are on the right track.
I've been onboard UAD since before they released the 1st Pultec eq (2005???) and I'm really happy with them. I now have 2 x solo cards and that does me as my main plugins are the V2 1176LN comps, Cambridge eq, Moog filter, Cooper Time-Cube and the EMT-140. Some stuff like the Fatso & Massive Passive use a big chunk of DSP which might be a concern for some users work flow & studio practices. Having a quad would eliminate that to some degree.
Having a mix of UAD and some quality native offerings is the way to go IMO. I'm sure stuff like 'the drop' filter plugin will compete sonically with the UAD Moog filter for example but I've been using the Moog for the past few years and the drop still hasn't been released as V1.00 yet!!!
Once you get your card, you can demo all the plugins for 14 days without restrictions (no noise burst or gapped audio) which all get reset after each plugin purchase. So by buying plugins one every 14 days, you can really test the range before spending any cash. Of course this can backfire and you end up wanting them all but using restraint and common sense, you should end up with a nice set of 'weapons of choice'.