Honestly Andy, Ultramarines are perfectly fine. And their largely neutral/central position as the benchmark space marine chapter arguablyt gives them more flexibility in terms of personality options. Chapters like the Dark angels, space wolves and black Templars all tend to be very samey, ironically its the least 'by the book' chapters that tend to have the least diversity in personality of their members. They are all basically the same barring a few exceptions or minor deviations. And most people just don't like ultramarines because of Matt Ward(one of the lore writers/ designers who has a hard-on for that chapter), its more appropriate to say that they don't like Matt than it is to say that they don't like the ultramarines. In my experience that is what 90% of people admit too when you actually question them on the subject.<br/><br/>They are a good baseline, and as a newbie to the franchise they are probably your best bet for a character as it wont force you towards any pre-disposition in terms of viewpoints or leave you as particularly antagonistic towards any other character because of their chapter. You also don't have crazy genetic flaws to deal with that you probably aren't going to be familiar with anyway as a newcomer. the ultramarines have pretty stable mentally and physically and you are less likely to start ripping out throats and guzzling blood, or one of a dozen other possible quirks.