The difference between DVI and Analog vary from monitor to monitor
However, no matter how good the convertors, converting Digital --> Analog --> Digital will result in signal degragation.
I think Samsung uses fair high quality parts in thier monitors in general, so if you aren't sensitive the lack of DVI wouldn't bother you. Personally, I wouldn't get a monitor without a DVI contection, if only to be able to connect two sources to the monitor at once.
Also, don't underestimate the importance of a good stand. The Samsung 915 is a nice fast monitor with a good price. But the 915 also uses a TN panel. TN panels generally have very poor viewing angles which makes the ability to adjust them easily even more important.
A side note, TN panels also have two other limitations. They are typically only 6-bit, which generally results in less colors. The panel is cable of displaying significantly less color, but through the majic of dithering is able to approach the display of 8-bit panels. TN panels also have fairly poor black levels in comparison to a PVA or MVA panel type. Although no LCD approaches CRT quality in this area, the difference between say 0.3 black and 0.5 black is very important in dark games.
The Samsung 915 is a good monitor, but only if the inherit limitations are acceptable.