I *love* mine - it almost always Just Works. Since all you do is buy
the enclosure (around $30), you can put in whatever size 2.5" drive
you'd like. I threw in a 750G, so I have ~98G of CD and DVD images.
There is a physical rocker switch for navigating the list of ISOs and
mounting/unmounting them. You can also toggle ISO-only, drive-only,
or hybrid/both mode, so I've got lots of other stuff on there that's
handy once you've booted. It also has a physical read-only switch -
The only hangup I've seen so far is if the BIOS doesn't support
USB-attached optical drives. There are probably some workarounds for
that out there (boot from a USB and then chainload-ish the optical
drive), but I have not yet pursued them.
There is undocumented support for floppy images as well. I haven't
tested it, but there are success stories.