I frequently encounter most of the problems in the poll and on numerous occasions. CoD4 is a very broken and unbalanced game but it is not unique in this (it probably seems worse than it is because I was promised the online gaming equivilent of sex when in reality is was somewhat mediocre and average), other games posess some of the problems CoD4 (I am yet to play WaW) has but the aforementioned 'other games' are typically not as well publicised or popular so CoD4 serves as a fine example of what we should not include in an online shooter:
1) awkward spawning system, we have all been the victim of a spawn killing wanker on one occasion but sometimes in CoD4 it is clear that the game itself has it in for you and will (on more occasions than can be explained by 'it's just a fluke') spawn right next to a grenade blast or in the path of an airstrike or helicopter. Another issue is how you are often spawned a long distance away from your previous killer, this would be fine if it weren't for the fact that roughly 74% of people who play CoD4 will use a gun that posesses a longer range than yours, the problem here is self explanitory.
2) glitches and cheats, if I have to explain to you why glitches and cheats make a game unfair and unenjoyable for the rest of us then you are probably one of the sad individuals who uses them and (for some reason known to neither man nor beast) gets off on it.
3) overpowered weapons, I used to get pissed at the use of snipers in Halo and Unreal Tournament due to their semi-one hit kill ability, long range and excessive use but CoD takes this to the next level by allowing anyone to start with the biggest, baddest sniper they can get their grubby hands on from the word go in every game (at least in Halo you had to race for the only rifle avalible). Since there are so many weapons avalible it is inevitable that some will be favored since they are more effective (see the M16 and MP5) and you will end up with a huge number of players using them exclusively, this not only defeats the point of giving you a selection in the first place but also means that anyone who tries to be unique and use a weapon the like the look or sound of will often meet with instant death, and a lot.
4)perks, some perks are actually ok and make the game more interesting (slight of hand, last stand, eavesdrop, bomb squad) but then there are 'those' perks...you know the ones I mean (martyrdom, stopping power, UAV jammer, frag x3/claymore). These perks are adopted by most self proclaimed 'good' players and while they are effective they often gives players a significantly unfair advantage, granted, everyone else can also take them to even the playing field but like with the choice of weapons, doing this defeats the point of even giving us an option.
I personally think that shooting games were best back when it was just a simple matter of 'you have guns, they do too, shoot each other until the game ends' (back in the golden days of Unreal and Goldeneye), we tried adding perks, choice and complexity into the mix along with advanced mechanics and physics and to me it feels as if we've lost some of the fun that was there before (at least we get achievements for our efforts).