The bottom line is this. For an general use PC or HTPC (pushing a 720p HDTV), it would be suitable. HTPC use with a 1080i system may be a stretch and you might want a more capable GPU (as suggested by buzznut).
If you are planning on playing the latest game titles, you will need to step up a class to the 57XX or 58XX GPUs.
Essentially, it all depends on what you plan to do with the HD5450 to gain a good assessment of its capabilities and limitations.