I am not sure where your negative impression of Synology comes from, but their reputation is among the best and I can only confirm this. The reviews I have read were all excellent. In fact, I am so much satisfied with my Syno NAS and their service that I've been considering moving up the Synology NAS range. In terms of bug fixes and reliability, they even beat Apple, sometimes by a wide margin. And no, I don't work for them.
Similarly to what you have read about Synology, I have yet to read anything positive about Drobo. All reviews I have come across lament the sub-par performance for a particular price point, which is why I never gave them a chance. I have tried the low-end 2-disk Dlinks and Netgears and returned them after a few days due to slow albeit seemingly normal performance for that particular price range. All this was part of the reason why I decided to spend a little more on a more powerful NAS with faster CPU and write/read rates, and indeed, speeds are now 2x - 3x from what I got before -- using an out-of-the-box configuration.
My Synology DS410 (4-disk) runs 24/7 and is absolutely reliable, but this really is the minimum requirement for any NAS. What makes Synology truly great -- and I think most fellow users would agree with that -- is the constant evolution of its operating system. It's the only product I own that keeps getting more and more functions added to it -- for free. Its operating system (Disk Station Manager) is updated regularly. Check out the DSM page on their website. A few weeks back, they added VPN Server capabilities, so I can run my own VPN without having to run my Macs 24/7. Of course, it supports iTunes (and if I remember correctly they are working on an implementation of Airplay), Time Machine (worked perfectly out-of-the-box under SL and they are now working on an update for Lion due to Apple's changes in protocols). I also use its Squeezeserver software. There's more.
Don't loose too much time over the hardware side of things -- there's not much magic happening there and I don't see much difference across manufacturers. Pick your CPU/speed and price point. But take time studying the NAS operating system, and what you get for your money. This is where the difference is.