This work explores the performance of MIMO (multiple-input/multiple-output) systems in Rayleigh fading channels with co-channel interference (CCI) and thermal noise. We provide analytical expressions for the outage probability of maximal ratio transmission combined with one of two different receive antenna array schemes, maximal ratio combining (MRC) and interference cancellation (IC) via null steering of the array pattern. We derive the statistics of the signal to interference-plus-noise ratio (SINR) for each technique in a closed-form and obtain an integral expression to calculate the average bit error rate (BER) or symbol error rate (SER). Our results show the conditions under which IC yields significantly better performance than MRC and vice versa. We also determine the impact on performance of the number of antennas in the transmit array.