Love might turn out to be great, terrible, or something in between. This game doesn't tell us much, other than he's not as good as Aaron Rodgers at this point in his career and didn't ball out after half a week to prepare against a team that was in the superbowl the last two years. If he starts next week and doesn't look any better, it might be time to be a little concerned - but even that is probably premature.
Love was a late 1st round pick, which is where QBs that need some seasoning go these days. With the revamped rookie contracts, teams don't wait around until the 3rd or 4th round to grab QBs they think can start anymore. So comparing where Love was drafted to where Rodgers was drafted is apples vs oranges. This is crucial point that seems forgotten whenever the topic comes up - a lot of teams passed on Rodgers because they had starting QBs and didn't want to pay huge money to a backup. Remember, this was before the Jamarcus Russel debacle.
As others have mentioned, he's more or less a rookie, having had no training camp or preseason in year one. It will probably take until year 3 to know what he's capable of, and maybe until year 4 or 5 to know what his ceiling will be - which was also the case with Rodgers.
And if he sucks? Ah well, 30 years of HOF QBs was a pretty good run, and we'll be looking forward to the Russian roulette that is trying to find a franchise QB - like half of the teams in the NFL seem to be doing every year. All the more reason to appreciate the good times while they're here/appreciate what we've had in the past.