I was most interested in the new choruses and I must say I'm really happy with the new possibilities.
- The Vintage can be best used to give a little analog chorus fx which sounds great. When pushed This thing would be really cool on '80 style synths, leads an brasses.
- The Hyper is a really nasty beast which is great when you want an over the top effect. Probably would work well with certain dance music leads when applied lightly.
- The air chorus. What can I say about this thing. I love it. I think I'll kick out my girlfriend tonight and propose to this little wonder. Gives you a nice stereo sound without that wet chorus feel.
- Haven't played much with the vibrato, but from what I have heard in the samples it can give a little live to those otherwise slightly dull sounding sounds.
- The rotator is cool. Obviously nobody expects a 100% true leslie rotator sound, with all the analog nitty gritty that comes with it, but it certainly is a very useful tool.
- The cross over is soooooo incredibly sweet for mixing. Thanks for adding this.
Unfortunately in the short time I have tested the beta I have some issues:
- Switching between choruses mutes audio for a while or causes noise bursts. The latter especially with the air chorus. Probably work in progress.
- Timing of the arp is still off in my DAW. Occasionally the timing of notes is also off when looping or after some CPU hit (e.g. I opened another app or something). As this doesn't happen with any other (soft) synth, I'm pretty damn sure this is a VC problem.
I know Reaper is not officially supported, but as the user base of this magnificent DAW is growing every minute, I'm hoping the nice guys & girls at Access have planned to change this fairly soon 
FYI: Using Reaper 64bit, with 64bit VC. Win7-64bit, M-Audio Firewire (crap), Intel-i7-920, 12gb ram.