Er, they offer 1U+5GB for $15. As in... less transfer than most $5 hosting plans come with.
If you think 5GB is going to be enough for your server, go for it... but beware this catch in their TOS:
"For burstable bandwidth, customer will be billed for all overage at a rate of $1.50/GByte in $100 increments."
According to that, your 5GB package could quickly end up costing you $115 if you're not careful. 5GB is an extremely small amount of transfer. IMHO, it shouldn't really be considered for a colo server unless it's a secondary server that is mostly talking to a primary.