My Sam440ep with AmigaOS 4.1 is my main home machine.
The biggest problem I have with it is the broken FAT filesystem when using USB devices. If I want to share data between my Sam and a PC I have to use CDs or DVDs. Connecting a USB device with a FAT filesystem on it to my Sam and writing to it is almost guaranteed to corrupt the data. (It's fine if I only _read_ data off the drive, and it's perfect if I format the USB drive to SFS.) I hope that gets fixed very soon.
The other biggest problem (heh) wouldn't be a problem for most people, but I'm a bit of a cheapskate who doesn't want to spend $50/mo. on an Internet connection, so I am still using dialup. The Sam's serial port is 'incomplete' and can't do hardware flow control, and I get lots of lost packets. I have serious connection problems even with my Amithlon, Linux, and C=Amiga boxes, though, so I don't think the Sam's serial port is the only problem. We have very noisy phone lines in my area.
Mostly the experience is good. It's more stable than my Commodore-era machines and OSes, and it's easy to manage my photos with it. I have to use 'foreign' applications like AbiWord and Gnumeric via AmiCygnix for compatibility with the outside world sometimes, but that's OK. I'm glad I have that option!
I don't have to worry about memory anymore like I had to with previous machines. If AmigaKit had come out with its ZoRAM memory cards a few years ago I probably would have stuck with my A3K a lot longer.
I got weaned off of hardware-banging games and demos when I moved to Amithlon, so it was easy to move to AmigsOS4. I think that everything that worked on Amithlon worked on AmigaOS4 right from the start.
Emulation of classic Amiga hardware is a little slow (I have a 667MHz Sam) so I have to set E-UAE to skip frames on some games, but I do still have classic Amigas around the house in case I need to see silky smooth scrolling.
I'm not allowed to bring work home, which is the way I like it.
So it's OK that I don't have Visual Studio, though It sure would be nice to have something that nice on Amiga!
Anyway, for Amiga stuff, it's stable and fast and there's no problem finding compatible keyboards, mouses, monitors, DVD-ReWriters, power supplies, etc. It likes my Canon DSLR and I can use an external card reader to read the data from my digital camcorder. The Sam is too slow to play the high def. H.264 video, though.
Oh, there is one FAT-formatted USB device I haven't yet had problems with, and that's my crappy little Sylvania MP3 player. I seem to be able to move files to/from that thing with my Sam with safety.
Oh yeah, the OS4 version of The Digital Universe is awesome!
I'd like to have a portable Amiga, and I'm open to trying AROS and MorphOS and even switching over if either of those feels comfortable. I just haven't gotten around to trying either one yet.