No probs, it's safe!

As for the noise of the 808 - that's probably the Zip drive, which can be murder around guitars and microphones. Best solution is to move the input gear as far away from the 808 as possible. As for software, I use WAVES Restoration bundle, which is pretty pro stuff! But good to get rid of 60hz hum, white and pink noise and such.

Now you said 1 question - and I see #2

Optical is the only one that drags BPM's around, and it can very well be just MY configuration? The 808 keeps steady regardless, but other MIDI gear like a Yamaha FX550 that looks for a 'constant' MIDI clock really suffer. But then the FX550 is like 15 years old, and was intended to be driven by a beat box.
Pretty well every MIDI connection will have drift/delay these days, and most gear has 'error compensation' installed to keep things tight. The 808, you may see the BPM move slightly - is really rock solid!

And the UW500 is really flexable in being 'analog', or 'digital', and 'syncable'. The only other unit that looks good is Edirols latest and M-Audio's Firewire 410 - that's a freakin' SCHIZNIT! www.maudio.co.uk

But the UW500 is pretty stealthy still.