I fancied an 800 when they first came out (and before my credit cards/rating went into meltdown) - to replace my 500. But, the 500 is a huge improvement on the 305 in terms of aesthetics. It's a pretty dinky unit thet fits nicely on the centrepoint (Cinelli Ram bars) whereas anything bigger (305 or 800) would have been to heavy (possibly) and definitely too bulky so would have had to be mounted on the stem part of my bars
Having said that, if I could come to terms with the slightly untidy look of a big box on my stem I may just get one anyway.
And, if anyone fancies a Silver 500, buy a red one and I'll do you a swap (with cash