Is the tippmann 98 custom a good paintball gun?

They are ok, over the years there has been many markers released that will give better performance for the same price or give the same performance at a lower cost. Tippmann, for the most part, has not changed the design since its release about 20 years ago. The sad part is in 2004 when Ben Tippmann left the company the board made a few changes to make the marker cheaper to produce (however this was never seen in a price drop) such as plastic instead of metal power tubes and changing the makeup of the metals so they were easier to make but did not last as long. Overall they are still decent markers for beginners but there are a lot of others out there that will give you more for your money.