Er, yes... but Manny has already stated he is experienced in striking systems, so that's not what he's after here. I might suggest reading the posts, rather than blindly pursuing an agenda.
Manny, I'm going to be less enthusiastic than others here. Personally, I'm not a real fan of cross-training the way you're describing it, or for the reasons you seem to be using. Really, it comes down to what a martial art is, and how it achieves it's aims. A martial art is a congruent body of knowledge, a set of beliefs, values, and philosophies, giving it it's guiding principles and concepts, and expressed through it's techniques. Now, one thing that that means is that any martial art is considered, or designed to be at least, a complete set of answers to the question of violence (within the parameters of the principles of the art). And those parameters help define it's use, including whether it is a specialist or generalist system.
There has been a tendancy for people training in specialist systems to feel that their system lacksa certain element, say, grappling, or ground fighting, or weapon defence. And that may be very true, however the idea of learning another specialist system to cover that "gap" is not really the right idea. The problem is that each of these systems is a complete method of moving in and of itself, and to simply "tack" another complete system of movement onto it, which is often contradictory to the initial one, results in internal confusion, as your unconscious mind (under stress) can't pick which one to go with (and it always picks what it considers, or believes, to be the best of any two options... so at best, the learning of one of the methods proves to be rather wasted effort from that viewpoint).
For an example, let's use TKD and BJJ. While there are certainly some similarities, there are also some rather big differences, which can lead to far less success than just focusing on one specialist system, and ensuring that your ability to "lead" any situation into the place that system wants to be is kept up to scratch (which is the way specialist systems are designed to work, by the way, not by taking a bit of this, and a bit of that to fill in percieved gaps). The similarities include a focus on the hips, a highly emphasised competitive element, and the two being recent martial creations. However, the way the hips are used is very different, the sense of distancing is very different, the preference for techniques is very different, the sense of angling and timing is very different, the concepts of position/posture is very different, and so on.
Now, that isn't to say that cross-training is not a good idea, or beneficial. But it needs to be approached properly. The best way, I feel, is to train in another art that deals with an area you feel less-confident in, and use it to understand the other environment, then apply the principles, ideas, and concepts of your primary art to that environment. Especially if the reason you are cross-training is for self defence, as there's really little point in training for self defence in a way that actually takes longer to get what you're after out of it, and contradicts the training you've already gone through. So look to what the secondary art is designed to cover, typically for a striking, stand up system, it's best to look to a ground-based grappling system, such as BJJ, or wrestling. Something that focuses on stand-up grappling, such as a number of traditional Japanese systems, or Aikido, tends to be even more counter-productive.
